Apparatus, systems, and methods may operate to select a subset of sensor responses as inputs to each of a plurality of pre-calibrated models in predicting each of a plurality of formation fluid properties. The sensor responses are obtained and pre-processed from a downhole measurement tool. Each of the plurality of predicted formation fluid properties are evaluated by applying constraints in hydrocarbon concentrations, geo-physics, and/or petro-physics. The selection of sensor responses and the associated models from a pre-constructed model base or a candidate pool are adjusted and reprocessed to validate model selection.